1. Field of the Invention
The invention is related to a smart antenna and, more particularly, to a smart antenna with an adjustable radiation pattern.
2. Description of the Related Art
A traditional smart antenna technology is often achieved by an array antenna with a tunable phase shifters. Take a traditional four-element array antenna with a half-wavelength spacing as example. When the phase shifter of each antenna element differs from each other by 60 degrees, the radiation beam will move to nearly 20 degrees. For an array antenna, the shape of its radiation pattern or the null directions in the radiation pattern can be controlled by dynamically adjusting the phase shifter. However, the phase shifter which can be dynamically adjusted has a high cost, so that the bottle neck of this design method is the high design cost. On the other hand, the separation between two antenna elements in the array antenna is usually designed to be a half wavelength, so that the antenna is difficult to be designed to be miniature. The above various problems make the smart antenna unsuitable to be used in information electronic products.